save_start=false argument ignored for neural_ode solve

[jessebett]

Tested here: https://github.com/jessebett/DiffEqFlux.jl/blob/master/test/solver_options.jl

If you call neural_ode with save_start=false it still returns the start. I believe this needed to be overridden internally to get adjoint to work, but what is returned should respect this argument.

It is very common to run these solves only requiring the output to be saved. It would be nice if there was an option like save_only in this case would be the end of the timespan.

[ChrisRackauckas]

It's supposed to be handled right here: https://github.com/JuliaDiffEq/DiffEqFlux.jl/blob/master/src/Flux/layers.jl#L73-L88

[jessebett]

aha, I'm not touching that with options save_everystep = false, save_start=false